1. Field of the Invention
The present invention generally relates to a method of recording an optical disk and an apparatus for recording an optical disk, and more particularly, it relates to a method of recording an optical disk and an apparatus for recording an optical disk, which can reduce a crosstalk from adjacent record tracks.
2. Description of the Related Art
As an optical disk, to and from which information can be freely recorded and reproduced by a user, there are a write once type optical disk of metal pigment film type, a rewritable type magneto-optic disk, a phase changing type optical disk and so on.
FIG. 5 shows a record signal spectrum of a LDD (Laser vision Disk with Digital audio).
For example, if whole display screen is occupied by white signals (i.e. white level signals), the signals of the appeared portion of the display screen are modulated to 9.3 MHz, while the horizontal synchronization signal and the vertical synchronization signal at the portion outside of the display screen are modulated to 7.6 MHz.
FIG. 6 shows an optical MTF (Modulation Transfer Function) characteristic at the innermost portion of the disk of LDD type (linear velocity is 10 m/sec).
This MTF characteristic is shown such that the recording frequency (pit size) of the data recorded on the disk of LDD type, is set to the axis of abscissa and the signal amplitude at the time of reproducing the disk by an optical pickup for a LD (Numerical Aperture NA=0.53, wavelength .lambda.=780 nm), is set to the axis of ordinate. From this, it is understood that the signal amplitude of the synchronization signal (7.6 MHz) is about 1.65 times of that of the white signal (9.3 MHz).
Therefore, as shown in FIG. 7, the size of the record pit on a track TR.sub.2 for the synchronization signal of the optical disk also becomes about 1.65 times of that on a track TR.sub.1 (or TR.sub.3) for the white signal correspondingly. Thus, there arises a possibility that a crosstalk is generated because the reading light beam, which is reading the white signal on the record track TR.sub.1 (or TR.sub.3), also reads the pit information corresponding to the synchronization signal on the record track TR.sub.2, which is adjacent to the record track TR.sub.1 (or TR.sub.3). Especially, in case of reproducing an optical disk of CLV (Constant Linear Velocity) type, since there is a high possibility that the video signal such as a white signal is recorded on one record track adjacent to another record track on which the synchronization signal is recorded, the crosstalk may be considerably generated.
More concretely, when the crosstalk is generated due to the synchronization signal, the portion where the crosstalk is Generated, becomes a color different from the desirable color to be displayed (white) on a displayed image, so that the image is degraded in quality as shown in FIG. 8, which is a serious problem.